Locking devices for doors and gates are well known in the art. Many of these devices frequently comprise a cylinder lock and a locking bolt in a same housing, the lock generally adapted to move the locking bolt between a locked position (door is locked) and an unlocked position (door is unlocked).
A conventional cylinder lock generally comprises a cylindrical core inserted in a cylindrical hole inside a casing, the cylindrical core adapted to rotate inside the hole when a correct key is inserted in a key slot in the core. Typically, prior to insertion of the key, the cylindrical core is in a closed position with the locking bolt in the locked position. Insertion of the correct key and rotation of the cylindrical core to an open position causes the locking bolt to move into the unlocked position.
The cylindrical core generally comprises a plurality of vertical “key-pin” holes (typically 5 or 6 holes although more or less holes may be used) disposed along a portion of the length of the cylindrical core, and into which are inserted “key” pins of varying lengths. The key pins are generally rounded at an end to allow the key to slide over them with relative ease when inserted and/or removed from the key slot.
Vertically positioned in “driver-pin” holes in the casing and above (or below) the key pins are spring-loaded “driver” pins. Each driver pin generally corresponds to a key pin below it, and is adapted to be pushed downwards into the key-pin hole of the key pin preventing the cylindrical core from rotating when there is no key in the key slot. Occasionally, the number of driver pins may be greater than the number of key pins, as typically used in “mastered” locks (one key opens several locks). A locking mechanism as described is generally known as a “pin tumbler locking mechanism”. This type of locking mechanism is based on a misalignment in a shear line along a point of intersection of the cylindrical core and the casing when an incorrect key is inserted in the key slot (that is, the shape of the key when inserted into the key slot causes one or more of the driver pins to be pushed into the key-pin hole of the key pin below it, and/or causes one or more key pins to be pushed into the driver-pin hole of the driver pin above it) and the cylindrical core may not be rotated. When the correct key is inserted in the key slot, the key pins and the driver pins are positioned inside their respective key-pin holes and driver-pin holes so that the shear line is aligned and the cylindrical core may be rotated to an open position.
A drawback in conventional cylinder locks is that they generally occupy a relatively large portion of a door area so as to provide space for rotation of the cylinder core. Additionally, space may also be required to accommodate a transmission mechanism, such as for example a cam, adapted to translate rotational motion of the cylindrical core into linear motion of a bar which secures and releases the locking bolt. Occasionally, a problem may arise in applications where the door area available to the locking device is restricted and which may limit the use of the conventional cylinder locks.
It is therefore the prime object of the invention to overcome this drawback of conventional cylinder locks.
It is a further object of the invention to provide a novel locking device which provides similar locking characteristics as those of conventional cylinder locks yet occupies a smaller door area than that occupied by the cylinder locks.
It is still a further object of the invention to provide for a locking device wherein a pin-tumbler locking arrangement is used as part of the locking mechanism however operable by a longitudinal rather than rotational movement.